W3C home > Mailing lists > Public > www-rdf-interest@w3.org > December 2001

Re: what RDF is not (was Re: RDF/XML Syntax Specification (Revised) W3C Working Draft published)

From: <jos.deroo.jd@belgium.agfa.com>
Date: Fri, 21 Dec 2001 00:25:33 +0100
To: pfps@research.bell-labs.com
Cc: bwm@hplb.hpl.hp.com, mmoran@netphysic.com, dave.beckett@bristol.ac.uk, www-rdf-interest@w3.org
Message-Id: <OFB551EBC1.A2851F5A-ONC1256B28.007E1D15@bayer-ag.com>
[...]

> > Indeed (but...)
> >
> > Let's take graph1 (but not assert it)
>
> How (in RDF)?
>
> >   _:child gc:childIn _:family .
> >   _:parent gc:spouseIn _:family .
> >
> > and let's take graph2 (but not assert it)
>
> Ditto.
>
> >   _:aaa gc:parent _:bbb .
> >
> > and let's
> >
> >   o assume that bnode _:child is same thing as bnode _:aaa
>
> How (in RDF)?
>
> >   o assume that bnode _:parent is same thing as bnode _:bbb
>
> Ditto.
>
> >   o assert that graph1 logically implies graph2
>
> Ditto.
>
> > From the ``implies'' scope the bnodes in graph1
> > are actually universally quantified variables
> > (and in this case also the bnodes of graph2
> > but not in the general case, where they
> > are only existentially quantified).
> > That is a FOL entailment rule
> > which we can simply write as
> >
> >   { ?child gc:childIn ?family . ?parent gc:spouseIn ?family }
> >     log:implies { ?child gc:parent ?parent } .
> >
> > No?
>
> I really don't know what you are trying to get at here.
> Are you trying to show that RDF has some power that one might not think
> that it has?  If so, you need to show that all the steps above can be
> performed within RDF.

That is not what I was trying to do, sorry for the confusion.
I think I took consistent steps along the lines of

[[
  The use of the phrase "asserted triple" is a deliberate weasel-worded
  artifact, to allow an RDF graph or document to contain triples which
  are being used for some non-assertional purpose. Strict conformity to
  the RDF 1.0 specification [RDFMS] assumes that all triples in a document
  are asserted triples, but making the distinction allows RDF parsers and
  inference engines to conform to the RDF syntax and to respect the RDF
  model theory without necessarily being fully committed to it. RDF as
  presently defined provides no syntactic means to distinguish asserted
  from nonasserted triples, however, so the distinction can be safely
  ignored in the remainder of the document, which assumes that all triples
  in a graph are asserted.(To apply the subsequent results to RDF containing
  unasserted triples, it would be necessary to restrict the definitions to
  the sets of asserted triples in the graphs.)
]] -- http://www.coginst.uwf.edu/users/phayes/w3-rdf-mt-current-draft.html

and

[[
  Notice however that such a variable-binding process would only be
  appropriate when applied to the conclusion of a proposed entailment.
  This corresponds to using the document as a goal or a query, in contrast
  to asserting it, i.e. claiming it to be true. If an RDF document is
  asserted, then it would be invalid to bind new values to any of its
  unlabeled nodes, since (by the anonymity lemmas) the resulting graph
  would not be entailed by the assertion.
]] -- http://www.coginst.uwf.edu/users/phayes/w3-rdf-mt-current-draft.html

and log:implies as/is entailment

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 20 December 2001 18:28:25 GMT

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